The term “PM” used herein means platinum, palladium, ruthenium and, in particular, rhodium.
Various large-scale petrochemical processes are performed under homogeneous catalysis of PM complex compounds. Well-known examples of the latter include rhodium complex compounds; one specific example of such type of catalyst is the famous Wilkinson catalyst which is used in hydrogenations and hydroformylations, for example.
Residues originating from homogeneous catalyzed petrochemical processes comprise PM in the form of PM complex compounds and/or derivatives thereof. The derivatives are formed during the petrochemical processes over time by chemical conversion or decomposition of the original PM complex compounds; in other words, the homogeneous catalysts suffer from exhaustion over time. Petrochemical process residues comprise in particular distillation bottoms (distillation residues) of petrochemical processes such as, for example, hydrogenation, hydroformylation or other petrochemical reactions. Petrochemical process residues represent waste material comprising exhausted catalyst. The waste material is typically liquid and high-caloric. In the following, PM containing petrochemical process residues are also called PM oil, for brevity. The PM content within such PM oil waste material is relatively low and lies in the range of, for example, 0.01 to 0.8 wt.-% (weight-%), calculated as PM.
Due to their high value, it is desired to recover PM contained in PM oil; it is hence common practice to burn PM oil in order to obtain a PM-enriched residue material which can be further refined. To this end, it has been common practice to slowly inject PM oil, e.g. with a lance, into a suited container or pond that is located in a furnace, e.g. a pan within a furnace room. The PM oil is ignited in the container and burned. The combustion off-gas is transferred into a conventional abatement system. The combustion residues have a higher PM content than the PM oil. However, this state of the art combustion process exhibits various drawbacks and weaknesses. One weakness of this technique is its low combustion rate. The PM oil to be burned may foam up or build up a crust during its combustion. Once a crust sits on the PM oil, the combustion process is stopped and thus efficiency is reduced. Captured unburned PM oil may become a potential danger due to unexpected combustion if it gets into contact with oxygen when moving the hot container.